Supercharge-type fuel injection control system

ABSTRACT

A fuel injection control system is provided wherein the supercharging pressure in an inlet pipe is detected and compared with the fuel pressure by a comparator and a fuel pressure regulating electromagnetic valve is controlled by the output of the comparator, whereby the fuel pressure is increased in accordance with the supercharging pressure to reduce the ratio of the injection time duration at full load to that at idling and thereby to reduce the duration of the opening of a fuel injection valve. In this way, it is possible to accomplish a proper fuel injection without requiring any additional injection valve.

tlnite States Patent 11 1 1111 3,844,263

Endo et a1. Oct. 29, 1974 [54] SUPERCHARGE-TYPE FUEL INJECTION 2,818,847 1/1958 Mock 123 119 CE CONTROL SYSTEM 2,841,129 7/1958 Reggio 123/1 19 CE 3,705,572 12/1972 Bloomfield 123/32 EA [75] Inventors: Kunio Endo, Anjo; Kunihiko Negi,

Nagoya both of Japan Primary ExaminerWendell E. Burns [73] Assignee: Nippondenso Co., Ltd., Kariya-shi, Attorney, Agent, or Firm-Cushman, Darby &

Japan Cushman [22] Filed: Aug. 3, 1973 211 Appl. No.: 385,340 [57] ABSTRACT A fuel injection control system is provided wherein the supercharging pressure in an inlet pipe is detected Forelgn Application Pnomy Data and compared with the fuel pressure by a comparator Aug. 7, Japan 1 and a pressure valve is controlled by the output of the comparator, whereby [52] 123/119 C, 123/32 123/119 the fuel pressure is increased in accordance with the 123/139 Aw supercharging pressure to reduce the ratio of the inv 1 at t at [58] held of Search 123/1 19 1 19 32 and thereby to reduce the duration of the opening of a 123/32 AB, 139 1 139 Aw fuel injection valve. In this way, it is possible to accomplish a proper fuel injection without requiring any [56] References Cited additional injection valve.

UNITED STATES PATENTS 2 Cl 9 D 1 r in 1 r s 2,565,482 8/1951 1301211 et al. 123/119 CE aw g e lo 7 8 S S H INLET FUEL FUEL P1PE PUMP TANK 1 INJECTION SUPER VALVE CHARGING PREssuRE 4 9 DETECTOR t FUEL HIGH 2 PRESSURE PRESSURE DETECTOR FUEL PIPE COMPENSAT- 2 CIRCUIT Low PRESSURE l 3 FUEL PIPE 13 COMPARATOR SECOND PREssuRE j REGULATOR POWER 1' AMPLIFIER HRST PRESSURE L 6 REGULATOR k FUEL PRESSURE i ELECTRO- MAGNETIC VALVE PATENTEBI1N91974 31844263 INLET I FUEL 4 FUEL PIPE v PUMP TANK IO v i I H INJECTION SUPER VALVE CHARGING PRESSURE 4 9 DETECTOR 4 v Y FUEL HIGH 2 PRESSURE PRESSURE & DETECTOR L PIPE COMPENSAT- l CIRCUIT v LOW PREssu E q 3 FUEL PIPE T s j COMPARATOR 'SECOND PRESSURE 5 v REGULATOR PowER y PRESSURE 6 REGULATOR I FUEL PRESSURE ELECTRO- MAGNETIC- VALVE PATENTEflnmeslsm 3.844.263

sum ear 5 I FIG.. 2

' IF (SUPERC|-IARGING' PRESSURE) FIG. 3

' Ep (DETECTED SUPERCl-iARGING) who/59v Y PRESSURE VOLTAGE M259 m P 8 5B P lFuEL PRESS RE) PAIENTEDncrzs 1974 3,844,263

- sum 30! 5 I K001291874 WEN D summer 5 FIG." 6

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FIG. a"

ow 1 1 T P (INLET PIPE PRESSURE) FIG. 9" q imnwwmmm 6 E Pc (SUPERCHARGINGQPRESSURE') SUPERCHARGE-TYPE FUEL INJECTION CONTROL SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control system having a supercharging function.

2. Description of the Prior Art In a known type of fuel injection control system having no supercharging function, if the injection of fuel is effected in synchronization with the rotation of the crankshaft, the ratio of the injection time duration at idling to that at full load is l 3 5. Thus, if, for example, the injection time duration at idling is 2.5 msec, then, assuming that four times larger than this is required, the injection time duration at full load is msec. With this condition, if the system is provided with a supercharging function, the amount of fuel required at full load increases and thus the time required for injection at the full load may become about 10 times larger than that required at idling. For instance, although the value differs depending on the amount of supercharging, if it is assumed that the required injection time at full load is four times Iarger'than that at idling when there is no supercharging function, the injection time required at full load is eight times larger than that at idling when there is a supercharging function providing a supercharging effect of l atmospheric pressure.

However, such a large value of the ratio between the injection time at full load and that at idling, i.e., the injection rate ('r ,/1-,,,,,.) makes it difficult to construct the required pulse width modulating circuit for generating pulses which determines the injection times and there is also possibility that as the number of revolutions of the engine increases, there occurs a phenomenon that the succeeding series of injections starts before the completion of the preceeding series of injections and it is therefore impossible to effect the adjustment of fuel quantity. Such a large injection rate is also undesirable from the standpoint of engine operation in view of the response characteristic of the injection system, the effect of standing waves in the inlet pipe, etc.

In an attempt to meet these requirements, it has been proposed to provide a pair of injection valves for each cylinder so that while only one of the injection valves is used during engine idling, a change-over is effected in the course of increase in the engine load and eventually the injection of fuel is effected by the two injection valves at full load. This proposed attempt has the disadvantage of making the fuel injection control system complicated.

In an illustrative embodiment shown herein, the system of this invention comprises a supercharging pressure detector for detecting the supercharging pressure in an inlet pipe which is varied by a supercharging function, a fuel pressure detector for detecting the pressure of fuel, a comparator for comparing the outputs of the detectors, a fuel pressure regulating electromagnetic valve opened and closed according to the output of the comparator to regulate the fuel pressure, and injection valve means for injecting fuel at said regulated fuel pressure, and the system thus has a very useful advantage in that the fuel pressure can be increased in accor dance with the detected supercharging pressure to reduce the value of the injection rate, i.e., the ratio between the injection time at full load and that at idling and thereby to reduce the duration of the opening of the injection valve means, whereby the injection of fuel can be effected properly without increasing the number of injection valve means.

In another embodiment, the system of this invention further comprises a second mechanical pressure regu' lator comprising a spring and a pressure regulator valve and arranged in parallel with the first pressure regulator to control the variation of the fuel pressure below a predetermined value, and the system of this embodiment thus has a very useful advantage in that in addition to the advantage of the first embodiment, any abnormal variation of the fuel pressure due to for example a fault in the electric circutry can be prevented.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a block diagram showing an embodiment of a fuel injection control system according to the present invention.

FIG. 2 is a characteristic diagram of the supercharging pressure detector used in the embodiment shown in FIG. 1.

FIG. 3 is a characteristic diagram of the compensating circuit used in the embodiment shown in FIG. 1.

FIG. 4 is a chracteristic diagram of the fuel pressure detector used in the embodiment shown in FIG. 1.

FIG. 5 is a schematic view showing part in section the mechanical parts of the embodiment shown in FIG. I.

FIG. 6 is an electric wiring diagram of the compensating circuit used in the embodiment shown in FIG. I.

FIG. 7 is an electric wiring diagram showing the interconnections of the comparator, power amplifier and fuel pressure regulating electromagnetic valve used in the embodiment shown in FIG. 1.

FIG. 8 is an inlet pipe pressure versus valve opening duration characteristic diagram useful for explaining the operation of the embodiment shown in FIG. 1.

FIG. 9 is a supercharging pressure versus fuel pressure characteristic diagram of the embodiment shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will now be explained in greater detail with reference to the illustrated embodiment. Referring first to FIG. I, numeral 1 designates a supercharging pressure detector connected to an inlet pipe Ia connected to a supercharger which is not shown to detect the supercharging pressure in the inlet pipe la. The supercharging pressure detector 1 produces its output as shown by the characteristic curve of FIG. 2 and this detected output voltage is converted in a compensating circuit 2 as shown by the characteristic curve of FIG. 3 which is predetermined in accordance with the required pressure regulations, thereby providing a reference voltage for a comparator 3. Numeral 4 designates a fuel pressure detector for detecting the pressure of fuel and producing its output as shown by the characteristic curve of FIG. 4, with the detected output voltage also applied to the comparator 3. The comparator 3 receives the outputs of the compensating circuit 2 and the fuel pressure detector 4 and uses the output of the compensating circuit 2 as its reference voltage. Consequently, when the detected voltage of the fuel pressure detector 4 becomes higher than the reference voltage by the compensating circuit 2, the comparator 3 generates an output which opens a fuel pressure regulating electromagnetic valve 6. A power amplifier 5 for amplifying the output of the comparator 3 receives the output of the comparator 3 and generates an output sufficient to actuate the fuel pressure regulating electromagnetic valve 6. Numeral 7 designates a fuel pump for delivering fuel from a fuel tank 8 at a high pressure into a high pressure fuel pipe 9 which is connected to the fuel pressure detector 4 and an injection valve 10. The high pressure fuel pipe 9 is also connected to a first pressure regulator 11 and the fuel pump 7 and the first pressure regulator 11 is connected to a low pressure fuel pipe 12 leading to the fuel tank 8. Further, for safety purposes or assisting the compensating circuit 2 in the performance of its compensating action, a second pressure regulator 13 of the mechanical type may be provided in parallel with the first pressure regulator 11 so that the abnormal rise of the fuel pressure may be controlled to a predetermined value by the second pressure regulator 13. The pressure regulator 11 is actuated by the pressure regulating electromagnetic valve 6 and therefore the electromagnetic valve 6 is generally constructed integral with the first pressure regulator 11.

FIG. 5 is a schematic view showing part in section an arrangement of the mechanical parts of the embodiment shown in FIG. I and the injection valve is provided between the inlet pipe la and the high pressure fuel pipe 9. The fuel pressure regulating electromagnetic valve 6 is provided in the first pressure regulator 11 and the output signal of the power amplifier 5 is applied across its input terminals 6a and 6b. The second pressure regulator 13 which may be provided in parallel with the first pressure regulator 11 comprises a spring 13a and a pressure regulator valve 13b.

FIG. 6 is an electric wiring diagram showing one form of the compensating circuit 2 used in the embodiment shown in FIG. I and it comprises diodes 2a, 2b and 2c, capacitor 2d, resistors 2e, 2f, 2g, 2h, 2i and 2j and operational amplifier 2k. The output voltage of the supercharging pressure detector 1 is applied to an input terminal 2! and a positive power supply voltage is applied across power supply terminals 2m and Zn, so that the compensation voltage shown in FIG. 3 is generated at an output terminal 20.

FIG. 7 is an electric circuit diagram showing an arrangement of the comparator 3, the power amplifier 5 and the fuel pressure regulating electromagnetic valve 6 used in the embodiment shown in FIG. I. The output of the compasating circuit 2 is applied as the reference voltage to an inverting input terminal 3b of a voltage comparator 3a and the detected output voltage of the fuel pressure detector 4 representing the fuel pressure is applied to a noninverting input terminal 3c, whereby when the detected fuel pressure voltage becomes higher than the reference voltage, a comparator output is generated to conduct a transistor 5a of the power am plifier 5 and thus a coil 60 of the electromagnetic valve 6 by the power supply voltage applied to the power supply terminal 6b.

With the construction described above, the operation of the system according to this invention will now be explained. In FIG. 8 showing the relationship between the pressure P in the inlet pipe Ia and the duration 'rof the opening of the injection valve 10 calculated on the basis of the fuel quantity delivered by a single injection, the curve b indicates the required characteristic of the duration 7 of the opening of the injection valve versus the pressure P in the inlet pipe when the fuel pressure is maintained constant and the value of the injection rate is large, whereas the curve a indicates the required characteristic of the valve opening duration 1 versus the inlet pipe pressure P when the fuel pressure is increased with increase in the supercharging pressure and the value of the injection rate is small. In this case, in order to obtain the characteristic represented by the curve a with small value of the injection rate, it is necessary to arrange so that the relationship between the supercharging pressure P and the fuel pressure P becomes as shown by the characteristic curve of FIG. 9.

For this reason, the output of the supercharging pres-.

sure detector 1 shown in FIG. 2 is converted by the compensating circuit 2 of FIG. 6 as shown by the characteristic curve of FIG. 3. Thus, with the provision of the comparator 3, the power amplifier 5 and the fuel pressure regulating electromagnetic valve 6, when the output of the fuel pressure detector 4 or the detected fuel pressure voltage becomes higher than the output compensation voltage of the compensating circuit 2, the fuel pressure regulating electromagnetic valve 6 is operated to reduce the fuel pressure in the high pressure fuel pipe 9. When the fuel pressure is reduced so that the detected output voltage of the fuel pressure detector 4 becomes lower than the output compensation voltage of the compensating circuit 2, the operation of the fuel pressure regulating electromagnetic valve 6 is stopped. Repetitions of this process control the pressure in the high pressure fuel pipe 9 at predetermined values dependent upon the output compensation voltage of the compensating circuit 2. Accordingly, the characteristic curve shown in FIG. 9 is obtained in accordance with variations of the supercharging pressure. By improving the response characteristic of the supercharging pressure detector 1, the compensating circuit 2, the comparator 3, the fuel pressure detector 4, the power amplifier 5, and the fuel pressure regulating electromagnetic valve 6, the opening and closing operation of the fuel pressure regulating electromagnetic valve 6 is effected and therefore the pressure in the high pressure fuel pipe 9 is regulated according to the predetermined pattern.

We claim:

1. A supercharge-type fuel injection control system comprising a supercharging pressure detector for detecting the supercharging pressure in an inlet pipe which is varied by a supercharging function, fuel pres sure detector for detecting the pressure of fuel to be injected, a comparator for comparing the outputs of said detectors, a fuel pressure regulating electromagnetic valve in a first pressure regulator adapted to be opened and closed in accordance with the output of said comparator to control said fuel pressure, and fuel injection valve means for injecting fuel in accordance with said regulated fuel pressure.

2. A supercharge-type fuel injection control system according to claim 1 further comprising a second mechanical-type pressure regulator comprising a spring and a pressure regulator valve and provided in parallel with said first pressure regulator to control variation of the fuel pressure below a predetermined value. 

1. A supercharge-type fuel injection control system comprising a supercharging pressure detector for detecting the supercharging pressure in an inlet pipe which is varied by a supercharging function, fuel pressure detector for detecting the pressure of fuel to be injected, a comparator for comparing the outputs of said detectors, a fuel pressure regulating electromagnetic valve in a first pressure regulator adapted to be opened and closed in accordance with the output of said comparator to control said fuel pressure, and fuel injection valve means for injecting fuel in accordance with said regulated fuel pressure.
 2. A supercharge-type fuel injection control system according to claim 1 further comprising a second mechanical-type pressure regulator comprising a spring and a pressure regulator valve and provided in parallel with said first pressure regulator to control variation of the fuel pressure below a predetermined value. 